1. Technical Field
The present invention relates in general to an improved disk drive, and in particular to an improved apparatus and method for protecting disks in a disk drive from head shock-induced errors and damage.
2. Description of the Related Art
Generally, a data access and storage system consists of one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. Disks are rigid platters that are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, two or three disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).
The only other moving part within a typical HDD is the actuator assembly. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
Typically, a slider is formed with an aerodynamic pattern of protrusions (air bearing design) on its air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each platter and flies just over the platter's surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single armature unit.
Each read/write head scans the surface of a disk during a “read” or “write” operation. The head and arm assembly is moved utilizing an actuator that is often a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which the spindle is also mounted. The base casting is in turn mounted to a frame via a compliant suspension. When current is fed to the motor, the VCM develops force or torque that is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head approaches a desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop directly over the desired track.
Disk drive sliders are susceptible to micro-cracks, fissures, corner-rounding, and edge-rounding effects due to the shock that results from the sliders landing on the disk from a load/unload platform. Disk damage may ensue when sliders come into direct contact with the disk surface when the slider air bearing has not been well established. This is typically seen in shock events, e.g., when loading heads onto the disk surface from a load/unload platform. For this reason, a disk area near the load platform is usually not qualified to be a data zone since the shock caused by errors in loading the sliders onto the disk causes dings and scratches in the media.
In addition, non-operational and operational z-axis shock can also create head and disk damage due to the high deceleration forces that occur when the disk drive is bumped or dropped during operation. This problem is especially true of mobile drives. To protect the sliders and disks from these shock events, an improved technique is needed that will aid in shock protection, and minimize wear and scarring events that happen when the slider contacts the disk at high speeds.